1. Field of the Invention
This invention relates to an injection molding unit comprising a coupling device for use in an injection molding machine for processing synthetic materials, comprising a rotatable and axially displaceable feed screw mounted in a detachable plasticizing cylinder and a drive device constituting a part of the injection molding unit comprising a spindle coaxially arranged with respect to an injection axis. The coupling device is provided for coupling the feed screw with the spindle by at least one axial locking means subject to a rotational movement, whereby at least one locking element constituting a pare of the locking means is received in a seat detachably connected to said drive device and turned towards the feed screw.
2. Description of the Prior Art
A coupling device of this kind is known from U.S. Pat. No. 4,704,078. In this coupling device the rotational movement of a motor is transmitted to a spindle which again transmits this rotational movement on to the feed screw. A radial coupling for the torque transmission and an axial locking means for driving the feed screw during the axial movements required during the injection cycle are provided for coupling the feed screw and the spindle. Two diametrically arranged slides, which are uncouplable by a radially catching expanding key, are provided as axial locking means. The spindle is penetrated by a driving pin, which ensures that the driving ring of the slide housing surrounding the slides, is pulled during the rotational movement. However, the driving pin is arranged in such a way that itself and consequently the slide housing is only removable once the girder bridge has been dismounted. This means that extensive mounting labor is necessary in order to gain access to the bearings of the spindle and the drive shaft for example.
U.S. Pat. No. 4,846,652 discloses an automatizable coupling device in which for coupling of the feed screw a rotatable slide is fixed in a driving piece by means of a cover screwed on the spindle of the motor. However, in practice it has turned out that the two linked pieces of this thread connection are pressed together so strongly that they can only be released with great difficulty.
Further coupling devices of this kind are known from German Patent 32 29 223. In these devices it is always necessary no remove the spindle in order to make possible an exchange of the bearings of the spindle of the motor.